Formal Charge and Radicals

[Samantha Burmester 3H]

Is the formal charge the determining factor of where to form an expanded octet on an element? For example, if there are two elements in the Lewis structure that are n=3 or below, what formal charge would indicate where to place the expanded octet?

[Diviya Khullar 1G]

When we are drawing a Lewis structure for a molecule, we want the formal charges of each atom to equal 0 or to equal the overall charge of the molecule. Often times determining which atom will carry a positive or negative formal charge depends on how electronegative the element is. For example, oxygen is highly electronegative atom, so in most cases it is preferred to have oxygen carry the negative formal charge and give it the electron.

[Mona Lee 4L]

Essentially, if the formal charge does not add up to the overall charge of the molecule, that lewis structure is not valid. Then, you can use process of elimination to figure out where to expand the octet.